random_well512a_simd/RandomWELL512a_SSE2.cpp

// Copyright (c) 2013, Peter Pettersson
// All rights reserved.
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#include "RandomWELL512a_SSE2.h"
#include <stdlib.h>		// Needed for rand().
#include <memory.h>		// Needed for memcpy().

RandomWELL512a_SSE2::RandomWELL512a_SSE2(int seed)
	: index(0)
	, resultIndex(4)
{
	srand(seed);
	for (int i = 0; i < 16; ++i)
		xmm_state[i] = _mm_set_epi32(rand(), rand(), rand(), rand());
}

RandomWELL512a_SSE2::RandomWELL512a_SSE2(unsigned *seed)
	: index(0)
	, resultIndex(4)
{
	for (int i = 0; i < 16; ++i)
		xmm_state[i] = _mm_set_epi32(seed[i + 48], seed[i + 32], seed[i + 16], seed[i]);
}

void RandomWELL512a_SSE2::GetUnsigned4(unsigned *result4)
{
	unsigned index_15		= (index + 15) & 15;
	__m128i state_index		= xmm_state[index];
	__m128i state_index_9	= xmm_state[(index +  9) & 15];
	__m128i state_index_13	= xmm_state[(index + 13) & 15];
	__m128i state_index_15	= xmm_state[index_15];
	const __m128i kMix		= _mm_set1_epi32(0xda442d24);

	__m128i left = _mm_xor_si128(state_index, _mm_slli_epi32(state_index, 16));
	__m128i right = _mm_xor_si128(state_index_13, _mm_slli_epi32(state_index_13, 15));
	__m128i z1 = _mm_xor_si128(left, right);
	__m128i z2 = _mm_xor_si128(state_index_9, _mm_srli_epi32(state_index_9, 11));
	__m128i result0 = _mm_xor_si128(z1, z2);
	xmm_state[index] = result0;

	__m128i result1 = _mm_xor_si128(state_index_15, _mm_slli_epi32(state_index_15, 2));
	result1 = _mm_xor_si128(result1, _mm_xor_si128(z1, _mm_slli_epi32(z1, 18)));
	result1 = _mm_xor_si128(result1, _mm_slli_epi32(z2, 28));
	result1 = _mm_xor_si128(result1, _mm_xor_si128(result0, _mm_and_si128(_mm_slli_epi32(result0, 5), kMix)));
	index = index_15;
	xmm_state[index] = result1;

	_mm_storeu_si128((__m128i *)result4, result1);
}

void RandomWELL512a_SSE2::GetDouble4(double *result4)
{
	unsigned unsignedResult[4];
	GetUnsigned4(unsignedResult);

	const double kToFloat = 2.32830643653869628906e-10;
	for (unsigned loop = 0; loop < 4; ++loop)
		result4[loop] = unsignedResult[loop] * kToFloat;
}